vshn/k8up

= How to Manage pod resources

There are 3 different levels how pod resources can be managed.
Each level takes precedence over the previous one.

. Global defaults
. `resourceRequirementsTemplate` field from a `Schedule` object
. `resources` fields in a `Backup`, `Prune`, `Check`, `Archive` or `Restore` spec within a `Schedule`.

[NOTE]
====
Global defaults are only applied through `Schedules`.
If you create your own `Backup` object for example, neither global default nor any specs from `resourceRequirementsTemplate` from any `Schedule` will be applied.
====

[IMPORTANT]
====
The computed resources resulting from the merge described above are not persisted in the `Schedules`.
This allows cluster administrator to reconfigure global resource defaults without having to touch each `Schedule` after a change.
====

== Global default

Let's assume the cluster administrator or a resource quota requires to set memory limit on a all pods spawned by K8up.
In that case K8up needs to be started with the following environment variable:
[source,bash]
----
BACKUP_GLOBAL_MEMORY_LIMIT=200M
----

TIP: See xref:references/operator-config-reference.adoc[Operator Config reference] to see which environment variables are supported.


Following example is a simple `Schedule` example without further resource specs.
[source,yaml]
----
apiVersion: k8up.io/v1
kind: Schedule
metadata:
  name: schedule-test
spec:
  ...
  prune:
    schedule: '*/5 * * * *'
----
This will create a `Prune` object with the resource default applied:
[source,yaml]
----
apiVersion: k8up.io/v1
kind: Prune
metadata:
  name: schedule-test-prune-qbq2k
spec:
  ...
  resources:
    limits:
      memory: 200M
----
This object in turn spawns a `Job` with the given resource spec.

== Resources from a template

Following example is a `Schedule` example that also sets CPU request for all jobs.
[source,yaml]
----
apiVersion: k8up.io/v1
kind: Schedule
metadata:
  name: schedule-test
spec:
  resourceRequirementsTemplate:
    requests:
      cpu: "50m"
  ...
  check:
    resources:
      requests:
        memory: "64Mi"
        cpu: "250m"
    schedule: '@hourly-random'
  prune:
    schedule: '*/2 * * * *'
----
Combined with the global memory limit, the `Prune` object will have following resources:
[source,yaml]
----
apiVersion: k8up.io/v1
kind: Prune
metadata:
  name: schedule-test-prune-qbq2k
spec:
  ...
  resources:
    requests:
      cpu: "50m"
    limits:
      memory: 200M
----
Whereas, the `Check` object will overwrite the CPU resource request template with its own specification:
[source,yaml]
----
apiVersion: k8up.io/v1
kind: Check
metadata:
  name: schedule-test-check-q5kae
spec:
  ...
  resources:
    requests:
      memory: "64Mi"
      cpu: "250m"
    limits:
      memory: 200M
----